Category: Evolutionary Biology

Paleontologists have discovered the fossil remains of a new hominin species in a dark cave system in South Africa and published their preliminary results in eLife. The new species has been named Homo naledi, which means “star man” in Sotho, after the Dinaledi Chamber of the Rising Star cave system where it was found. Homo naledi is characterized by a small body and brain size, but it also features several adaptations of the hands and feet that are relatively similar to modern humans. The age of Homo naledi and its position in the phylogenetic tree of hominins is still unresolved, but it is believed to be one of the more primitive ancestors of mankind. So far, an unprecedented 1550 remains of at least 15 individuals of Homo naledi have been unearthed, representing the largest fossil assemblage of a single hominin species ever found in Africa. Given the richness and exceptional preservation state of these fossils, it is speculated that Homo naledi may have been capable of performing primitive burial rites.

Scientists at the University of Bonn have found pigments in fossilized eggs of dinosaurs, which indicates that dinosaurs may have laid colored eggs similar to modern birds. The scientists performed organic geochemical analyses on well preserved, 66 million year old fossil remains of eggshells belonging to the oviraptor Heyuannia huangi and discovered the presence of the pigments protoporphyrin and biliverdin. These pigments are known to be responsible for the blue and green colors in present-day robin and emu eggs, respectively, which suggests that the studied oviraptor eggs may have had blue-green colors as well. It is believed that these oviraptor eggs were laid in partially open ground nests and therefore, their blue-green coloring may have provided a means of camouflage against predators. This study is the first to reconstruct the color of dinosaur eggs and provides a link between the reproductive biology of dinosaurs and the evolutionary traits inherited by modern birds.

New findings of scientists from several universities published in Science show that the Permian-Triassic mass extinction (~ 252 million years ago), the greatest extinction event of all time, was caused by ocean acidification. The researchers studied boron isotopes from marine sediments in order to reconstruct seawater pH and subsequently combined these data with quantitative modeling techniques to develop a scenario for the mass extinction. Their results show that seawater pH remained relatively stable during the first phase of the extinction, but rapidly shifted to more acidic values during the second phase, which lasted ~ 10 thousand years. This acidification of the oceans had dramatic consequences for life on Earth and is thought to be associated with the release of massive amounts of carbon, related to the volcanism of the Siberian Traps. Up to 96 % of living marine species became extinct during the Permian-Triassic mass extinction and now, it has been shown for the first time that ocean acidification was the responsible mechanism.

Research of biologists published in Global Change Biology indicates that emperor penguins on Antarctica were forced into refugia by extreme cold during the last glacial maximum (~ 19.5 – 16 thousand years ago). By comparing the DNA of fossil emperor penguins with the DNA of living individuals and colonies, the scientists were able to reconstruct the population dynamics of emperor penguins on Antarctica through time. Their results show three mitochondrial clades within emperor penguins at the time of the last glacial maximum, which suggests that these birds were isolated in three small, separate populations and may have survived in refugia such as the Ross Sea. The population sizes of emperor penguins are related to the balance between sea ice available for breeding and open water available for foraging. Sea ice extent around Antarctica was much greater during the last glacial maximum than at present and therefore, reduced food availability resulted in severe losses among populations of emperor penguins.

Geologists of different universities have found that insufficient levels of atmospheric oxygen during the mid-Proterozoic (~ 1.8 billion to 800 million years ago) delayed the evolutionary rise of animals on Earth. They studied chromium isotope data from shallow marine Proterozoic sediments and compared them to younger Phanerozoic sediments deposited in similar environments. Their findings suggest that chromium oxidation in the Proterozoic was very limited and that oxygen levels were at most 0.1 % of present atmospheric levels. Previous estimates of atmospheric concentrations have varied greatly, but it was generally accepted that oxygen existed at Earth’s surface during the Proterozoic. The late appearance and diversification of metazoans was therefore long thought to be limited by genetic advancements and ecological innovation, but now it appears that their evolution was instead delayed by low levels of oxygen.

According to a new study performed by biologists, the current extinction rates of terrestrial animal and plant species associated with human activities may be up to 10 times higher than previously thought. By using fossil datasets and mathematical models, the scientists were able to estimate new natural background rates of species diversification and extinction. Their results indicate that until now, these background rates are likely to have been overestimated and should be in the order of 0.1 extinction per million species per year, rather than 1 extinction per million species per year. Because current rates of extinction are compared against background levels, these new results have major implications for the apparent impact of mankind on life on Earth: the effects may be even more severe than expected.